Downstream regulation of int gene expression by the b2 region in phage lambda

Epp, Chris; Pearson, Mark; Enquist, Lynn W.

doi:10.1016/0378-1119(81)90012-3

Cited by 22 publications

(12 citation statements)

References 43 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In a lysogenic response to infection, the Int protein for integrative recombination is produced from the PI transcript under positive regulation by A clI protein. In the lytic response to infection, the int gene is transcribed from the PL promoter under antitermination control by X N protein.However, Int protein is not normally produced as a consequence of a regulatory element, sib, downstream in the transcript from the int gene (3,11,14,30). This mode of control by a distal sequence is termed retroregulation (10,13,30).…”

mentioning

confidence: 99%

See 1 more Smart Citation

Retroregulation of the bacteriophage lambda int gene: limited secondary degradation of the RNase III-processed transcript

Plunkett

Echols

1989

J Bacteriol

View full text Add to dashboard Cite

Expression of the int gene of bacteriophage A from two promoters, PI and PL' is differentially regulated through RNA processing. Efficient Int protein synthesis from the PL RNA is inhibited by the action of sib, a cis-acting retroregulator downstream from the int gene. We have used mapping procedures with nuclease Si to study the PL transcripts produced in vivo after phage A infection. We have found an RNase r-dependent processing site within the Int coding sequence, 387 nucleotides upstream from the site of the primary cleavage by RNase m at Sib. This secondary processing site is located at the most stable region of secondary structure in the sib int region, as predicted by computer analysis. We suggest that RNase HI cleavage at the Sib site alows processive exonucleolytic degradation of the RNA to proceed to a region of secondary structure within the Int coding sequence, which protects the upstream region of the transcript from further degradation.Control of site-specific recombination by bacteriophage X involves differential expression of the tightly linked, partially overlapping int and xis genes from two promoter sites, PI and PL (10). In a lysogenic response to infection, the Int protein for integrative recombination is produced from the PI transcript under positive regulation by A clI protein. In the lytic response to infection, the int gene is transcribed from the PL promoter under antitermination control by X N protein.However, Int protein is not normally produced as a consequence of a regulatory element, sib, downstream in the transcript from the int gene (3,11,14,30). This mode of control by a distal sequence is termed retroregulation (10,13,30). The sib site provides for specific regulation of int; expression of xis and other upstream genes of the PL transcript is not substantially affected, and shorter aminoterminal fragments encoded by amber mutants escape sib regulation (30).The action of sib as a retroregulator depends on RNase III, indicating a posttranscriptional mode of regulation (3,13,15,30). The sib site has been defined, by deletions and point mutations, as a region of extended dyad symmetry physically overlapping but functionally separate from the t, terminator (7,15,25). RNase III cleaves the PL mRNA at this site both in vivo and in vitro (31). Given the location of this cleavage, 243 nucleotides downstream from the end of the Int coding sequence, it is evident that some additional event must occur to regulate Int production. The favored model for sib retroregulation involves secondary processing after the RNase III cleavage by 3'-to-5' exonucleolytic degradation proceeding from Sib into the Int coding sequence (10, 13, 15) (Fig. 1).RNase ITT-dependent processing site within the int gene. To look for the secondary processing of PL RNA predicted by the model, we have used nuclease S1 mapping (1, 4, 5). To avoid any potential artifacts arising from plasmid sequences (16), we analyzed the int transcripts within their normal genomic context by preparing all RNAs from phage-infected cells; th...

show abstract

mentioning

confidence: 99%

“…However, Int protein is not normally produced as a consequence of a regulatory element, sib, downstream in the transcript from the int gene (3,11,14,30). This mode of control by a distal sequence is termed retroregulation (10,13,30).…”

mentioning

confidence: 99%

Retroregulation of the bacteriophage lambda int gene: limited secondary degradation of the RNase III-processed transcript

Plunkett

Echols

1989

J Bacteriol

View full text Add to dashboard Cite

show abstract

“…However, infection with b2cII-results in high levels of int activity. This observation and other experiments led to the proposal of a site located, in the b region which selectively inhibits int expression from PL (17,18). We have named this site sib for sitio inhibidor en b.…”

mentioning

confidence: 99%

“…We also provide evidence to show that sib acts posttranscriptionally to prevent mRNA translation. Finally, we discuss the possible mechanism of sib action and the implication of sib in overall control of phage development.Unlike all previously analyzed prokaryotic control systems, in which the controlling sites are located before the structural gene(s), sib is located distal to the structural gene(s) (17,18). We shall call the process of control from beyond a gene "retroregulation" (19).…”

mentioning

confidence: 99%

See 1 more Smart Citation

Posttranscriptional control of bacteriophage lambda gene expression from a site distal to the gene.

Guarneros¹,

Montañéz²,

Hernández³

et al. 1982

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

The bacteriophage A int gene product, integrase, recombines the phage DNA with the host DNA at specific sites on each to accomplish lysogeny. The int gene is transcribed from two promoters, PL and PI, each regulated positively by A proteins. The expression of integrase is also controlled from a site, sib, in the b region of the phage genome. This is a unique regulatory site because it is located distal to the structural gene in relation to the promoters. The expression ofint from the PL promoter is inhibited when sib is present. This effect appears to be specific for PL because sib does not cause inhibition of PI-dependent int synthesis.A mutants that contain alterations in the site have been isolated. Sequence analyses of the mutations reveal single base changes, spanning 37 base pairs (bp) in the b region, some 240-bp beyond the int gene. Another mutant, hef13, which has a phenotype similar to that of sib, introduces a nucleotide change within the same 37-bp region. The sib and hefmutatsons cluster within a region of dyad symmetry. Regulation of int synthesis by sib occurs after transcription.of the int gene. There is no difference in the rate of .PL'promoted int mRNA synthesis in either sib' or sib-phage infections, yet int mRNA is less stable in the sib' infection. Because RNase 111 host mutants are defective in sib regulation, processing of the PL mRNA at sib by this endoribonuclease may cause int mRNA decay and decrease int synthesis.Bacteriophage A inserts its DNA into the Escherichia coli chromosome as part of the process leading to lysogeny. This integration event uses A int protein and occurs by reciprocal recombination at specific locations, named "attachment sites," in the phage (attP) and in the bacterial (attB) DNAs. The reversal of the integrative reaction is excision; this process occurs after prophage induction and allows the integrated DNA to dissociate from the bacterial chromosome. The two phage proteins int and xis are required for excisive recombination. Host factors are also required for both integration and excision, but the direction of the reaction depends primarily upon the presence of int or int and xis in the cell (1-3).Two promoters, PI and PL, control transcription of the 1.5-kilobase int-xis region (4, 5) (Fig. 1). Both promoters are positively regulated by different effectors. Gene N product allows elongation of the PL transcript through several genes into the int-xis region (11,12). The cII product is required to initiate transcription from PI by facilitating initiation by RNA polymerase (7). The PI promoter overlaps with the xis gene, and its transcript does not include all of xis (8-10). Thus a differential expression of the integration and excision systems is assured by turning on and off PI or PL Infections with cII-phage result in decreased int protein levels and integration activity (13)(14)(15). This result is unexpected because transcription initiated by RNA polymerase at PL was thought to extend through thexis-int region (11, 16). However, infection with b2cII-...

show abstract

Retroregulation of Bacteriophage λ int Gene Expression

Guarneros

1988

Current Topics in Microbiology and Immunology

View full text Add to dashboard Cite

Downstream regulation of int gene expression by the b2 region in phage lambda

Cited by 22 publications

References 43 publications

Retroregulation of the bacteriophage lambda int gene: limited secondary degradation of the RNase III-processed transcript

Retroregulation of the bacteriophage lambda int gene: limited secondary degradation of the RNase III-processed transcript

Posttranscriptional control of bacteriophage lambda gene expression from a site distal to the gene.

Retroregulation of Bacteriophage λ int Gene Expression

Contact Info

Product

Resources

About